Objective In general, refining units involved in thermomechanical pulp processing consume (depending on the quality of required paste) 1,800KWh/t. of produced paste, 90% of which is turned to heat during the process and dissipated as steam. This project aims to recover and recycle waste steam (at 1.7 Bar) from the pressurised preheater for the fibre separator, to achieve energy savings.Equipment orders were placed in the first quarter of 1980 and system start-up one year later, with full operation since May 1981.When paste production is between 30% and 50% of maximum capacity and one defibering machine in use, only the smallest compressor, supplying an average steam output of 2t/h need be used. Between 50% and 80% of maximum output with two defibering units in use, the largest compressor is required, supplying average steam output of 2t/h. When paste production is between 80% and 10% and both defibering units in use, both compressors are required.During the first six months of 1982 the cost per ton of produced steam, based on reduced values was FF20.12 in comparison with FF100/t for steam produced by the main station.Recorded data over the same period show : - steam recovery of 9,320t: - 857,440KWh electricity consumed: - FF1,160/t average fuel price: - FFO.2187KWh average price: - FF543,000 savings.Prospects for replication are favourable particularly in the paper making industry. For example, in the drying room drainage system it would have the following advantages over systems currently in use : - independent battery adjustment: - when drying special papers the number of batteries may be increased: - energy saving, since all steam blown is immediately recovered and used without substantial flow increase (similar to thermo-compressors)Thermomechanical pulp production has been increased over the past decade due to a fall in raw material costs, lower chemical pulp consumption and improved characteristics. It is however, an intensive consumer of electricity.An innovation in the Beghin-Say process is in the use of water ring compressors in which steam is constantly saturated by direct contact with the water ring during compression phase. Water ring and compressed steam pressure are maintained at the same level, by being recirculated. Steam generated by the process contains various wood acids, resins, some air and solid particles, small shavings and, due to the possibility of clogging, is difficult to recuperate.Process steam is extracted from the preheater via an automatic valve operated in series with the existing preheater and fed to a cyclone washer where heavier particles are seperated out on the continuously sprayed internal walls. Finer particles are removed when the steam passes through a fine water curtain sprayed from the upper part of the washer.Solid particles seperated from process steam are removed by floatation, condensates being drawn-off through the automatic valve just below the monitored water lever in the cyclone washer. Additionally, atomized water in the upper part of the cyclone washer is vitually cleared of all solid impurities, the atomiser pump being supplied from the lower part of the tank from the cyclone washer, where treated condensates from the exchangers exist. The water volume required to wash the chips when entering the preheater is reduced since the condensates containing solid particles are recycled in the process.Exchangers acting as heat pump evaporator consist of removable stainless stell plates arranged to provide vertical ducts where preheater steam freely condenses while boiler condensates evaporate in a cross-flow system.Excess condensate is continuously pumped from the first separator, returning simultaneously with the evaporated steam, whichimproves heat transfer on the evaporator side.Two water ring compressors operate either in parallel or series, the largest of 1,00Kg-2,500Kg/h. capacity, the smaller of 700Kg-1,300Kg/h. capacity : installed electrical power is 132Kw and 55Kw respectively. Temperature between outlet and inlet is 10 deg.C - 14 deg.C for both compressors. System flexibility, instant start-up and shut-down is achieved by the pump supplying the exchangers and the pump supplying the water rings for the compressors being kept permanently in service. The steam throughput perfectly matches that of the outlet process steam without affecting preheater pressure (an essential characteristic of the process).The exchangers are designed for a 5 deg.C temperature variation at maximum output and 3t/h evaporation, keeping compression low as possible and maintaining exchanger wall temperature as near as possible to that of process condensating steam. Programme(s) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Topic(s) 1.6 - INDUSTRY Call for proposal Data not available Funding Scheme DEM - Demonstration contracts Coordinator PAPETERIES BEGHIN-SAY EU contribution No data Address 62112 CORBEHEM France See on map Total cost No data
